Metallurgical process



Sept. 7, 1954 A 7' 7' ORA f 75 Patented Sept. 7, 1954 'METALLURGICALPROCESS Julius D. Madaras, Detroit, 'Mich., assignor to 'Madar'asCorporation, Wilmington,-Del., a corporationof Delaware ApplicationNovember'l, 1949, Serial No125934 12 Claims. 1

My invention relates to a method of creating very'high temperatures in avessel by means 'of the exothermic heat of formation of two or morematerials. In my method, a substantial part of the amount of heatliberated is utilized for supplying the heat quantity necessary toraisethe temperature of the charge to'a very "high degree, and forcarrying on chemical reactions between two or more substances that reactto a substantial degree only at veryhi'gh temperatures and where thereaction is endothermic. The use -of the heat of exothermic'reaction forsupplying the needed amount of heat for carrying on the endothermicreaction also serves for controlling the temperature.

Some of the heat absorbing reactionsan'd'preheating of the 'materialsare performed separately, as far as it is practical to performthem, inother vessels before the reacting and other materials are broughttogether for final reaction; so that as much heat credit is added to thematerials as is practical and desirable.

A suitable apparatus for carrying out my'new process is illustrated inthe drawings. 'The'n'umeral H] designates a la'dle'or crucible-dike ap-'paratus having a steel shell or casing'll which islined on the insidewith carbon blocks'or a solid dense carbon wall 12. 'A lining ofrefractory material is provided between the casing and carbon lining 12,the type and construction'of said refractory lining "depending upon theprocess to be carried out within the ladleand'the'materials available.Anyone familiarwithhandling molten metals-can easily determine what typeof lining is best in each case; howeverjas specifically illustrated, therefractory consists of "a layer of high temperature-material 13 next tothe carbon 12 and a layer of refractory material of low thermalconductivity I l'next'to' the steel casing. An iron tap hole I and aslag tap hole 16 are provided near the bottom 'ofthe ladle, however boththe iron and slag may be withdrawn through the same hole if desired.Also, with the type of construction illustrated, the molten materialsmay be poured out through a spout l1, however any other suitableconstruction of ladle and lining may be used without departing'from myinvention.

A refractory lined door or cover [8 is fastened to the top of the ladleby a suitable hinge I9,

and one or more suitableclamps 20 are'provided for holding the coverclosed. The door may be solid asshown or may be formed-as a-lattice workor :some other construction.

A plunger 2| is located -within theladle'an'd is rovided with anoperating rod'or stem 22 which extendsup'wardthroug h an aperture in thecover. The plunger is preferably constructed of perforated metalJprot-Ectedby means 'of' a refractory layer 23"whi'ch is provided withsuitable apertures' 24 permitting escape of gases.

If a solid door or cover is used, a suitable refractory lined opening 25is provided therein to permit pouring of molten "metal or other materialinto the ladle without opening the door. In some cases, where the ladledoesnot have to be covered, a ring'frame forholding the plunger may besubstituted for the door. Theplu'nger 2! may be of any construction bestsuited for the particular operation to be carried out'as willhereinafter'be described. Any suitable means (not shown) may be'operably connected to the stem 22 for operating the plunger.

One or more openings 26 are provided in'the side of the ladle as a.means'of introducing liquids or gases into the ladle, however in somecases such liquids or gases may be introduced through either of the tapholes l5 and 16 or through the opening 25 inthe cover.

Into the ladle are put alternate layers of preheated hot sand or lumpscontaining mostly alumina, some silica and "whatever other metallicoxides there are in it,=and' of hot lime. These layers are separated bylayers of carbon between them. Either intothe lime or into thealuminasand orat any suitable-place there are lumps or briquettes or grainymetallic -0Xid8 or oxides mixed with carbon? preferablyain a. hot state.

As illustrated, the bottom layer 2'! consists of carbonaceousmaterial;which may be in the form of coke, crushed charcoal' 'or othertype of carbon. 1

On top ofthe carbonisa layer of hot lime-'28 which may have somecarbonmixed therewith if desired, and which-is covered by a thin'layer ofcarbon on top. Next comes a layer of hot alumina sand =29 which ma'y"contain any desired amount of silica along with other metallic oxideimpurities. This layer may have some carbon intel-mixed if de'sired,--and is -also covered by a thin top layer of carbon. Also,-o'thermetallic oxides and carbon maybe added to this layer in the formof-pellets or'briqu'ettes. Over'the layer 29 is a layer of'charcoal 3ilsimilar to bottom layer 27, and the-layers-are repeated in the abovedescribed order to'fill the ladle to any desired height. Afill ofcharcoal 3| "on top of the last layer completes'thecharging of theladle.

It will be understood that the above constitutes but one method"of-charg'ingthe materials into the ladle, and thatthe composition ofthematerials such as ores, fluxes and fuels may vary a great dealdepending upon the particular operations being carried out in eachinstance. Some of the greatest economic and operating advantages of myinvention are due to the fact that lower grade ores, fuels and othermaterials may be used in my process in the same condition in which theyare mined than can economically and practically be used in otherprocesses. The products produced by my process will meet the widelyvarying requirements of analysis, quality and other specialcharacteristics demanded in industry.

The required quantities of oxides and carbon in the mixtures, as well asthe relative amounts of sand, lime and other materials, will depend uponthe specific analysis of materials to be used and results to be achievedin each particular instance and for each particular purpose. specifiedcase, any person versed in the art of melting or of metallurgy will beable to calculate and determine the requirements according to themethods of calculation to be hereinafter described.

After the ladle is properly filled and the door or cover is closed, hotmolten metal, such as molten iron, for instance, is poured into theladle. In contact with the carbon layers, the hot molten metal startsabsorbing part of the carbon. Also, some agitation is soon developedwhich, in addition to the absorbing of some of the carbon, brings thehot lime or other basic oxides together with the hot acid oxides. Theacid oxides may consist partly of silica, but preferably the greaterpart will be present as alumina. Slag begins to form quickly. The heatof slag formation is so high that it raises the temperature of the slagand other materials in the ladle to an exceedingly high degree. Forinstance, the formation of calcium silicate slag (CaOSiO2), releasesabout 372 B. t. u. per lb. of slag or 770 B. t. u. per lb. of limereacted. The specific heat of this slag is about 0.23 B. t. u. perdegree F per 1b., which would be sufficient to raise the temperature ofthe slag alone by about 1,620 F.

The reaction between lime an dalumina, however, in forming slag releasesapproximately 1,460 B. t. u. per lb. of slag consisting of 2CaO'Al203 or2,800 B. t. u. per lb. of lime, which would be enough heat to raise thetemperature of this slag alone by more than 6,000 F. This great heatcreates more boiling and agitation bringing together more and more basicand acid oxides (lime and alumina, for instance) from the differentlayers, the hot molten foamy slag working upward and in all directionsso that the slag formation is quickly completed. During this time theplunger is holding down the charcoal, if so desired, to carburize themolten iron, to cause the reducing reactions to proceed in presence ofcarbon and to prevent the violently boiling slag splashing out of theladle.

It should be noted that excessively high temperatures do not actuallydevelop in practice. This is possibly because the oxides and othercompounds reach the temperature where they dissociate or will notassociate until the excess heat is used, thereby checking thetemperature rise, and partly because the reactions such as reducing theoxides with carbon as described above will check the rise of heat andmaintain certain heat balances.

In general, with my invention, the generation of heat, the temperaturesdeveloped, the reduction of In each specific amounts of specifiedoxides, the degree of carburization, the production of products andby-products such as slag for making alumina or cement and other featuresare under control, and the operations are performed under control.

The figures given above are only approximate, but are adequate forperforming the needed calculations and to describe and illustrate theworking of my invention.

A substantial part of this heat of exothermic slag formation isavailable for supplying the needed balance of heat for the carbonaceousreduction of metallic or other oxides, while the endothermic reducingreactions occur in presence of carbon. The carbonaceous reduction ofsilica (SiOz) to Si will illustrate the method of calculation and methodof operation.

In forming calcium aluminate slag as shown above, approximately 1,460 B.t. u. per lb. of slag is liberated. Let us assume that the materialsoriginally mixed in the ladle have been brought to 2,500 F. It is wellknown that in presence of carbon silica reduces to silicon very rapidlyin the temperature range of 3200 F.- 3500 F. Assuming that the slagtemperature remains at about 3500 F. raising all materials to thistemperature absorbs about 300 B. t. u. per lb. of slag and there is aheat loss of about B. t. u./lb. of slag, leaving 1,060 B. t. u., or inround figures 1,000 B. t. u. per lb. of slag for supplying the heat forendothermic reductions. The reduction of silica therefore will proceedas long as there is silica and carbon present and the slag is not cooledbelow a stage where silica no longer will reduce. An example will makethis clearer.

Assuming a total of 100 lbs. of lime-alumina slag, approximately 100,000B. t. u. of useful heat for reducing S102 is liberated by the slagformation. In round figures 7,000 B. t. u. net is absorbed by reducingone lb. of silicon with carbon from SiO2. Therefore with 100 lbs. ofslag, approximately 14 lbs. to 15 lbs. of silicon is reduced. If thereis more silicon in the slag it will stay combined in the slag as SiOzunless more lime is added, or lime and alumina as may be required by theacidity of the slag, because the reduction of silica cools the slag to atemperature where the silica will not reduce rapidly enough. It isevident that the reduction of silica comes to a balance or heatequilibrium and also controls or balances the temperatures of the slagand of the molten metal and carbon. Care should be taken that the slagis of such acid composition that it releases the silicon at theparticular temperature of operation. The heats of reaction of slagformation of any particular slag analysis are easily calculated.

In a manner similar to the reduction of silica, practically all othermetallic oxides may be reduced With carbon, the heat of formation ofslag supplying the needed amount of heat. The temperatures at which thevarious oxides reduce in presence of carbon and their heats of reactionare known to any metallurgist or melting operator versed in the art, andalso may be found in technical books. In order to facilitate thedescription and clarification of my invention, approximate heats ofreaction and practical approximate temperatures of reaction of some ofthe most common lower and higher oxides will be given here.

Iron: FeO to Fe at 1900 F. 2,060 B. t. u./lb. Fe. Manganese: MnO to Mnat 2900 F. 3,800 B. t. u.;

MnOz to Mn7,600 B. t. u.

Silicon: S102 to Si at 3200'F. I2,900-B.it. u.

Vanadium: V203 to V at 3100 F. 5,800-B. t. u.

Molybdenum: M002 to M0 at approx. 3000 3,300 B. t. u.

Copper oxide at very low temperature, 1080 B. t. u.; titanium fromtitanium oxide at 3500- F. 71-00 B. t. u. chromium from its oxide at4500 F. 4720 B. t. u. These values are per pound metal. Temperatures ofreduction and negative heat of reaction vary somewhat, according towhatspeed of reaction is desired orassumed. From these heat values,approximately 3270 B. t. u. should be deducted for each pound of oxygenliberated from the oxide and combined with carbon to form CO. In eachparticular instancethe oxygen combined with a 1b. of metal is calculatedfrom the atomic weights.

A simple example will suffice to illustrate the case. The atomic weightof iron is 56 and of oxygen is 16; therefore 16/56 lbs. or 2/7 lb. ofoxygen is combined with every pound of iron when oxidized to iEeO. Whenthis oxide is reduced with carbon this amount of oxygen therefore willcombine with the carbon and release approximately 935 B. t. u. Thissubtracted from 2,060 B. t. u. gives. 1125 B. t. u. which must besupplied. This, of course, assumes that only 00 will form which isactually the case in such high temperature reduction. In each instancethe heat generated by the oxygen combining with thecarbon will varysomewhat and can be easily calculated by the analysis of the gasevolved.

By a further example I will show the specific method of calculating theheat needed to reduce silicon from the lime-silica-aluminate slag. AS-sume roughly that the aluminate slag is in the form of CaO AlzOs, whichgives 100 B. t. u. per pound of slag or 2840 B. t. u. per lb. of lime.Also assume that the silica slag is in the form of CaOSiOz, which gives372 B. t. u. per 1b. of slag or Z68 B. t. u. per lb. of lime. Thereforethe difference of heat generated by the slag forming reaction with a lb.of lime under the above conditions is 2840768=2072 B. t. u. From theatomic weights it is calculated that every 28 lbs. of silicon reducedwill set free 56 lbs. of lime, or 2 lbs. of lime per lb. of silicon.This lime, when recombining with alumina generates 5680 B. t. u. heatand therefore gives 2 2072=4,l44 B. t. u. heat credit. Similarly, with28 lbs. of silicon, 32 lbs. of oxygen is combined, or 1.17 lbs. ofoxygen per lb. silicon, which from the previous figures, when combiningwith carbon gives 3270 1.17:3820 B. t. u. per lb. of silica. This withthe heat credit obtained from the slag adjustment gives approximately7964 B. t. u. heat credit, or 8,000 B. t. u. in round figures. The, heatof formation of SiOz is 13,000 B. t. u. from which by subtracting the8,000 B. t. u. heatcredit 5,000 B. t. u. per lb. of silicon theoreticalheat requirement is obtained. Now, while the heat losses in the processof reducing silica by my method is comparatively very small, 1000 B.'t.u. loss per lb. of silicon may be assumed. This added to the theoreticalheat requirement makes the total net heat requirement 6,000 B. t. u. perlb. silicon.

It should always be borne in mind that even under the same conditionswith approximately the same kind and analysis of materials the slag andtemperature conditions will always vary. This is characteristic of allsimilar reducing, melting and smelting operations. There is much morevariance, however, when materials of highly 6 difieringranalysissandztemperatures :are changed in the various instances. In such operationscalculationsiare onlya guide to help determine theeapproximate'valuesand requirements. The essential characteristics of my-new invention arethat by following my method of operation'the required or desiredmaterials will be obtained With-great savings in both labor andmaterials,

and different and higher qualities, along with,

many 'other advantages, will be attained. In every instanceand. to eachoperator versed in the art of melting, smelting and'similar operations,these calculations and'descriptions will give an adequate guide todetermine his operations so that by:following my method of operation andby usin myequipment he will obtain savings and other-benefits.

In every instance, heretofore or hereinafter described, it should beborne in mind that there isno specific temperature to which the lime orother materials are to be heated in order to follow my method. However,any heat added to'the materials will be so much more heat available forthe reactions at higher temperatures. For instance; the specific heat oflime is 0.23 B. t. u./F. Therefore it requires the addition of 460 B. t.u. toheata pound of cold lime to 2,000 F. Therefore, if the lime ischarged cold about 460 B. t. u. is to be subtracted from the balance ofthe heat of slag formation that may be applied for accomplishing otherreactions as previously shown. The average specific heat of sand isapproximately 0.25 and that ofthe iron oxide approximately 036. Fromthese and similar available dataany required or needed heat calculationsmay be made.

These examples give the method of calculation for each specific case.Since the different alumina sands and difierent metallic oxides contalnvarying amounts of iron oxides, manganese :oxide, titanium oxide andother oxides, it is possible only by analysis Or approximation of allthe reacting materials to calculate how much carbon is to be mixed inand how much metal will be reduced from its oxide, or sulphide or otherchemical combination.

The oxides will reduce in the order of their places as determined by theelectro-potential series of metals. For instance, practically all ironoxide will be reduced first, then will follow manganeseand then siliconreduction. The reduction proceeds as long as there is enough carbonpresent, and there is oxide to be reduced and there is enough heat tosupply the heat needed at any particular temperature for the continuanceof any particular endothermic reaction. Whenever-there is no carbon orno heat available, theoxide that could otherwise have been reduced willremain as part of the slag. When there is no oxide available that couldbe reduced at a particular temperature the available heat will raise thetemperature of the slag and the carbon that is submerged into it andwill heat some of the iron until all come to a temperature equilibrium.

My invention of a method for treating oxides is also a new method ofpreparing calcium aluminate from various grades of bauxite. The bauxiteore is heated to drive out the moisture and the combined water. The ironoxide usually present is partially or fully reduced, or if -so desired,no reduction of the iron oxide is performed. The hot dehydrated bauxiteore is then charged into the-ladle or crucible together with alternatelayers of carbon, lime,"carbon and ore,

in any suitable sequence as previously described, and the top is coveredwith charcoal or other form of lumpy carbon. The reaction is startedeither by pouring molten slag or molten metal into the crucible, or byblowing hot air into it through the tap hole. The air burns with thecharcoal creating intense heat and also bringing the acids and basicslag forming materials together. When the reaction has a good enoughstart to progress by itself, the indication of which will be theformation of molten slag, the tap hole is plugged in any known manner.The slag will be forming, creating intense heat and raising thetemperature of the slag and of anything in contact with it. Charging hotcharcoal instead of cold charcoal speeds up the slag formation andenhances the progress of reactions. The hot slag. boils and rises, thusfurther speeding the reaction. When the temperature is high enough,around 2000 F. for instance, the iron oxide contained in the mixturequickly reduces wherever it is in contact with carbon. The unreducediron oxide forms a part of the slag and is reduced from the slag bycoming in contact with carbon. The reduction of each pound of ironreduced from FeO to Fe absorbs roughly 1,000 B. t. u. net.

When all the iron oxide is reduced the temperature rises further to arange where any manganese oxide which may be present is reduced. Thetemperature will then rise to a range over 3000 F. where the reductionof silica to silicon progresses rapidly. The molten iron, manganese andsilicon flow down to the bottom forming a metal bath, and if desired allor any part of it may be removed at the different stages of operation toobtain the desired combination of metals. The hot charcoal is pusheddown into the slag, or even into the metal bath and the reduction of thesilica to silicon proceeds as long as there is silica available andthere is heat available from the heat of slag formation to supply theneeded heat to carry on the endothermic reaction of reducing silica tosilicon. When there is no more silica to reduce, the temperature risesto a degree determined by the available remaining heat. If there areother higher oxides in the mixture, when the slag temperature reachestheir range of reduction with carbon the reduction of the higher oxideproceeds, checking the rise of temperature. tent is so high that thereis not enough heat produced by the slag formation to reduce all of thesilica, the reduction stops at whatever temperature is reached, and theremaining silica stays as a combined part of the slag. If all or most ofthe silica content has been reduced and heat is still available, moresilica or other desired suitable oxide or oxides may be added to utilizethe excess available heat for the reduction of these oxides.

As shown before, the reduction of each pound of silica requires roughly7,000 B. t. u. The exact theoretical amount, of course, corresponds tothe heat of formation of the oxide, minus the heat of the formation ofthe evolved carbon monoxide and of a small amount of carbon dioxide andthe available heat provided by the liberated lime due to reduction ofsilica to combine with the lime-aluminate. The radiated and conductedheat losses are, of course, losses from the net,

heat created by the slag formation.

Some more silica may be reduced from the molten bath if necessary byblowing very hot carbon monoxide or hydrogen into the slag through theopenings 25 or 26, or through the If the original silica con- 8 tapholes l5 and Hi. This, however, cools the slag quickly and no morereduction can be done without added heat.

When the desired reactions are completed, the molten metal and slag aretapped 01f through tap holes [5 and [6. The remaining unabsorbed hotcarbon that was on top will descend to the bottom and will serve as thebottom layer of carbon in the new pile as described above, or part of itmay be removed.

After all or most of the iron oxide, silica and other contents that areconsidered as impurities, are reduced out of the mixture, the slagremaining will be concentrated molten calcium aluminate (CaOAlzOs) whichforms the material from which the substantially pure alumina isseparated to be used for the manufacture of aluminum and for other uses.The lime is recovered to be used over again in forming new alumina slag.

My invention also includes a process for making substantially purealumina for the manufacture of aluminum and is described and carried outas follows:

As previously described, the bauxite ore or other suitable high aluminacontent ore together with the included impurities are preheated to ahigh predetermined temperature and charged into the ladle with a properamount of preheated lime and carbon, preferably charcoal, and smelted asheretofore illustrated.

The degree of preheating of the charged materials and the amount of limecharged depend in each instance upon the amount and nature of theimpurities contained in the charge, as previously explained.

In the smelting process the metallic oxides are reduced and separatedand recovered as valuable metals and the remaining slag becomessubstantially pure calcium aluminate.

This calcium aluminate slag is then treated with sodium carbonate(NazCOa) solution in water whereupon the lime (09.0) is regenerated intocalcium carbonate (CaCOs) and precipitated out and will be recalcinedand used again to form new slag with additional heated bauxite.

The remaining solution consists of sodium hydroxide (NaOH) and water,and alumina. Into this solution carbon dioxide (CO2) which is obtainedfrom the recalcining of the recovered calcium carbonate or obtainedotherwise is introduced into the above solution, thereby precipitatingthe alumina. The sodium carbonate solution is recovered and used overagain in the cycle of treating more calcium aluminate. The commerciallypure alumina is dehydrated by the application of heat in a known manner,and is a valuable product in the manufacture of aluminum by electrolysisor by other suitable processes.

My invention has great industrial and economic advantage over all otherknown processes including those where sodium hydroxide and sodiumcarbonate are employed to precipitate the calcium carbonate andmanufacture aluminum mainly because the impurities such as iron andother oxides and especially silica are separated and extracted in thesmelting as valuable metals, also, the formed calcium aluminate slag isof substantially high purity as compared to calcium aluminate slagproduced by other processes, which slag contains a rather objectionableamount of silica.

Obtaining calcium aluminate in a substantially pure form especiallywithout objectionable silica content results among other advantages inthe.

following great economic and technological advantages:

The sodium hydroxide and sodium carbonate solutions are greatlyconcentrated as compared to the concentration of solutions used by otherprocesses where approximately only two or three pounds of alumina, forinstance, can be practically dissolved in a ton of solvent withoutdissolving too much silica with the alumina and thereby excessivelycontaminating the solution with silica.

Using my process, it is practical to dissolve ten times as much or evenmore alumina in the same amount of solution, as can be successfullyaccomplished in other processes. This can be carried practically to thelimit of solubility of alumina. In contrast, the other processes willeither dissolve an objectionable amount of silica While trying todissolve more alumina, or, in order to reduce the silica content beforethe alumina isseparated, a separate and expensive treatment isnecessary. In my processno such separate silica treatment is required.

Furthermore, in other processes, eliminating even part of the silicafrom the slag wastes a great deal of time, alumina, and solvent,resulting in appreciable and serious material and economic losses.

My process also has the great advantage that it can use unconcentratedbauxite or alumina sand having a much greater content of silica andother impurities than it is practical to use with present processes.While at present there are only a few and meager amounts of commerciallyusable bauxite deposits throughout the world, there are vast deposits ofless concentrated bauxite practically in all parts of the world that arepractical to be used with my process and are not practical to be usedwith other processes without previous expensive concentration. Also myprocess extracts the silica in form of valuable silicon from theseso-called low grade unusable bauxite sands, while with the otherprocesses the silica is an expensive loss and a most objectionableimpurity.

In general, the overall economy of my process in producing metals, ironand alloys and commercially pure alumina, and ultimately substantiallypure aluminum from various bauxite ores is much greater than all otherknown processes.

The sequence of reactions is summarized as follows:

CaO.Al20a Nazc 03 1120 oacoi A1203 2NaOH 1120 A1zO3.2NaOH E20 CO2NflzCOa-+ E20 A1203 CaOOi heat :10 CO2 It is evident that when my methodis used in the above described manner, it is a new process for makingferro-silicon" from the iron oxide and silica of the bauxite ores andpreparing commercially pure or usable molten calcium aluminate ready formaking aluminum.

Without departing from my invention, the hot lime and hot alumina orewith its iron, or iron charcoal as previously described; It is alsoprac-10 tical, if so desired, to pour molten slag into the chargetogether'with the two streams of hot lime and hot sand.

The slag reaction in any desired case may be expedited by pouring backinto the crucible some of the molten metal'or molten slag produced andpreviously tapped out, instead of pouring new iron into the ladle. Inthis manner a higher alloy content f'e'rro alloy is produced. The ironcontent iscontrolle'd by analysis and selecting the proper bauxite or ifdesired, adding more iron.

In order to expedite the carbon-distribution in the hot aluminum ore andhot lime, after they are heated, if so desired, hot cracked natural gasor other hydrocarbon gas containing carbon black is 'passedthrough themfilling the pores-of the mass with carbon black; Partly cracked methaneor other hydrocarbon can be used to crackin the hot alumina ore, andalso in the hot lime, de positing the carbon black in the pores. Thecracked gas is ata very high temperature, possibly at about 2,500 F. Itwill-reduce most of the iron oxide and willv also supply the heat'forthe endothermic reaction'of cracking the hydrocarbon. Also, thesolidalumina and lime are hot and will give up some of the heat to thecracking gas. One ton of lime' will supply about 140,000 B. t. u.and'one-ton of alumina 180,000 B. t. u. when cooled 300 F. Five thousandcu; ft. of gas cooled from 2,500 F; to 2,000 F. together with the heatthe c'ontainedfree' carbon and of its 20% methane, for instance,supplies'about 65,000 B. t. u. This makes'a total of roughly"2l0,000" to220,000 B. t. u. which is enough to crack over 2,000 cu. ft. of methane,therefore more than. enough to crack the methane content of the hot gas.In this manner over lbs. of carbon black is deposited in a'ton of'alumina. and-about the same amount in aton of lime, making about "200lbs. carbon in two' tone of slag material. This carbon deposit alon'e'isenough to reduce 500 lbs. of silica to form 200* lbs. of silicon;provided the needed heat is supplied bythe slag formation.

The carbon to be supplied iseasily calculated in the following way: Whenthe alumina sand contains 10%, that is, 200 lbs. of silica perton ofsand, andthe lime to be used contains ab'out100 lbs. silica 'per tonlime, there is 300 lbs. silica to be reduced. This contains lbs.silicon, re quiring '120 lbs. carbon which is 3% by weight, of 4,000lbs. of reacting materials. When the deposited carbon is not sufiicient,the charcoal sunk in the molten slag supplies the needed balance ofcarbon.

When 4,000 lbs. of alumina and lime are brought together inproperproportion, as shown previously, roughly 4,000,000 B. -t. u.useful heat will be liberated. This is enough to reduce 5'72 lbs. ofsilicon from over 1,230 lbs. of silica which means about 30 %31% silicacontent of the combined weight of 4,000lbs.slag. Thisclearly illustrateshowimportant my new process is for making ferro alloys and highgr'a'demolten calcium aluminate not only from currently used grade of bauxitebut also from very'lo'w' grade and present non-commercial bauxite.

It is practical withmy' invention to apply'th'e above shown 4,000,000 B.t. u. of'useful heat for the manufacture oi iron and other metals "fromtheir oxides on'a commercial scale at a great economic advantage overthe other known proc'-' esses.

The iron ore is-p'reheated and preferably prereduced to the extent wherethe reduction with reducing gas is'fa'st, ea'sy an'd efficient. m somecases this stage of reduction in general, is desirable only to a stagewhere all the iron oxide is reduced to FeO, but in most of the cases itis easy and efficient to reduce the ore to a, point where approximatelyone-half of the iron oxide is metallized and the remainder is in theform of FeO.

This partially reduced hot iron ore is charged into the ladle orcrucible with the proper amount of carbon, hot lime and proper amount ofalumina content slag forming acid as previously illustrated. As it isknown, the addition of approximately 1,000 B. t. u. of heat is neededfor reducing one lb. of iron from FeO. Therefore, the 4,000,000 B.t.u.of useful heat mentioned above supplies the heat for the carbonaceousreduction of 4,000 lbs. of iron from FeO. Since with every pound of FeOone pound of metallized iron is also present, it is readily seen thatthe 4,000,000 B.t.u. are suflicient to supply the heat for themanufacture of 8,000 pounds or more of metallic iron where combined withthe separate partial reduction of iron ore. At the same time the formedslag will be useful for the manufacture of cement and, in someinstances, of high grade alumina for the aluminum industry or for otherpurposes. The extent of partial reduction of iron ore and the amount ofalloys reduced and manufactured in my process is easily determined ineach particular instance by following the illustration and informationgiven at several places in this specification.

Similarly, the process is used for preparing high alumina content cementby way of molten slag. The ratios of alumina, silica and lime are variedand controlled at will. The following description illustrates themethod.

A desired and controlled amount of hot lime and hot high alumina sandare brought together in the ladle in presence of carbon by either of themethods described above. As slag forms, heat develops and the ironcontained in the slag reduces and collects at the bottom, and also ifdesired, all or part of the silica is reduced. The slag when cooled isground to make cement in the usual manner. By selecting the propersilica and alumina content sand, or making the proper mixture of sand,and considering the composition of the lime, practically any desiredanalysis of slag is formed to make any commercial grade cement.

Thus it is readily seen that my invention is also a usable and veryeconomical method for the combined manufacture of iron and other metalsand cement.

If desired, all or part of the iron oxide contained in the hot sand andhot lime is reduced by passing hot reducing gas through it preferably inthe pulsating manner, described in my U. S. Patent No. 2,243,110. Whilereducing the iron oxide entirely or partially, or after it is reduced, adesired amount of carbon is also deposited in the sand or lime or both.Also, as previously described, carbon can be mixed in while charging thesand, silica and lime, or may be added separately. The sand and lime forthe purpose of making cement or for any of the purposes coming withinthe scope of my invention, are so selected or are so mixed that theultimate analysis of the slag satisfies the requirements for which it isintended, whether it is for cement, calcium-aluminate for makingaluminum or refining slag for iron, steel or other metals.

If the sand, bauxite and lime as naturally found, does not give therequired composition of slag or develop the required heat for thepurposes intended, instead of adding the required lime or sand orbauxite to the original mixture the balance of hot sand, hot alumina orhot lime or all of them may be added to the hot molten slag indetermined amounts. This method also comes within the scope of myinvention.

In forming Portland cement a great deal of silica content is required.This silica with lime gives only approximately 372 B. t. u. per lb. ofslag, which, however, is enough to raise the temperature of both by overl,600 F. while the contained calcium aluminate slag adds about 1,400 B.t. u. per pound of slag. When high silica slag is to be formed it israther important that most of the iron oxide content of the sand shouldbe fully or partially reduced as may be desired, since there is not muchsurplus heat for iron oxide reduction when preheating the sand asdescribed previously.

Furthermore, my method of utilizing the generated heat of slag formationfor useful purposes, such as melting or reducing lower or high oxidesinto their metals or both, is also used for melting hot sponge iron witha considerable amount of gangue content, refining and carburizing theiron and reducing it into its alloys like manganese or silicon. Themethod is the following:

Hot carbon is charged into the bottom of the crucible or ladle, or hotresidual carbon is left in it: The carbon is covered with hot lime, thenwith a block or quantity of hot sponge iron which has a definite amountof gangue of definite analysis, requiring a rather predetermined amountof lime for fiuxing. Lime can also be charged around the sponge ironbetween it and. the wall of the crucible. In some cases hot alumina orcarbon or both is also added to the lime or on top of the lime or belowit for the purpose shown below. Lime and carbon may be added to thecharge in the ladle in any other suitable manner without departing frommy invention.

In cases where the hot sponge iron does not form a more or less solidblock but is broken up into lumps or is loose, like gravel or sand orpowder, while charging into the crucible, the lime and also some carbon,preferably charcoal, if desired, is mixed in with it. In many cases itis also desirable to deposit a predetermined amount of hot carbon in thehot sponge iron as previously described.

In order to start the slag forming reaction, hot air or oxygen enrichedhot air is blown through either tap hole to burn with the carbon. Afterthe hot alumina slag starts forming, it will liberate heat and the slagformation proceeds by itself. The hot slag rises taking lime with itthat further slags with the gangue of the iron, liberating heat andmelting the iron. The reaction of slag formation and melting thenproceeds rapidly and automatically, provided the proper amount of limeis present to form the proper hot fluid slag. Any person versed inmelting or smelting iron or any trained metallurgist is able tocalculate and determine easily the proper proportions of various acids,such as silica and alumina and bases such as lime, magnesia, etc. toobtain the proper slag and evolve the proper desired amount of heat.Some briquettes or pellets of a mixture of fine alumina and lime may beput in, if desired, right under the sponge iron or at any other suitableplace to start the hot slag formation and" therebyliberateheat. Anyother heat forming'mixture; for instance, such as magnesium and otheroxide, known, as thermit, is satisfactory and is added if desired tostart the slag forming reaction. In such a case, care should be takenthat the heat of formation is not too violent, does not lift or blow thecharge and does .not affect the vessel or the personnel. It is alsopractical in order to start and promote theslag formation to pourmolten'slag over the top of the sponge iron or into the lime at theside.

When the desired proportions of silica and alumina are not present in.the iron ore and consequently in the sponge iron to supply the heat formelting by the heat of slag formation, a predetermined amount of high.alumina sand is added to. the ore. Alternatively, hot high. alumina sandmay be added in the ladle orto the sponge iron while preparing thecharge in the ladle. Of course, enough hot lime is also added to formtheproper slag with the alumina sand or lumps. The alumina sand usuallycontains some silica.

Melting a ton of hot iron which. contains carbon from sponge iron,which. is at l800 R, and

raising its temperature to about 2,700 F. requires approximately 400,000B. t. u. This amount of heat is supplied by forming. approximately 350lbs. of calcium aluminate slag. Usually, however, there is more thanenough gangue of proper composition in the ore to supply the requiredheat of melting the hot sponge iron and slagging of the gangueby addingthe proper amount of lime to form the desired slag.

As an example of operation a typical washed East Texas ore illustratesthe case. The approximate analysis of the ore is 47% Fe, 11% A1203 and%S1O2. After this ore is reduced. to sponge iron at about 1,800 F., itrequires approximately 400,000 B. t. u. to melt a ton of iron containingcarbon and to raise it to 2,700 F. There are roughly 425 lbs. of silicaand 475 lbs. of alumina with 2,000 lbs. iron. Adding about 900 to 1000lbs. of lime forms 1,800 to 1,900 lbs. of slag. The 850 lbs. of calciumsilicate slag has 200,000 3. t. 11. heat of formation which. isliberated and the 950 lbs. of calcium alminate slag 1,300,000 B. t. u.liberated, making a total of 1,500,000 B. t. u. liberated and available,as follows: Assume the case where the lime is charged at 2,400 F. It

takes approximately 500,000 B. t. u. to raise the slag temperature byl,000 F. leaving. 1,000,000 B. t. 11. About half of this heat is used bymelting and raising the temperature of the iron, while the other halfmillion B. t. u. is available for reducing silica to silicon. Inpresence of carbon this will supply enough heat if desired to reduceabout 40 lbs. to '70 lbs. of silicon, which enters the iron bath, andwhich makes 2% to 3 silicon iron. The high temperature thus reached alsoserves to carburize the iron to ahigh degree. If

more heat is required, as mentioned above, more hot alumina is added andthe required: amount of lime or other suitable basic oxide with it.Similarly, manganese oxide is also reduced by the carbon. Heats ofreaction of other slags of any definite composition may be easilydetermined as previously explained and illustrated.

Thus the melting, as well as the silicon, manganese and carbon contentof the iron is controlled by the gangue content of the iron ore, by theamount of lime added and by the'temperatures of the materials, which is.the. total heat in the materials.

My process is used also for melting and refining solid scrap .or pigiron or steel or their mixtures.

The solid; iron or steel is preheated-'to-any desired temperature,forinstanceto about 1500 F. At the .bottom-;.ofthe ladle is placedsome-carbon and some hot lime or hot alumina. The hot solid iron ischarged into the ladle and a predetermined amount of hot alumina. sandand hot lime is added. Ifthe lime andalumina sand are not hot enoughtostart the reaction, some amount of hot molten iron is poured in whichwill start the slag formation that will proceed rapidly and come tocompletion generating. large amounts of heat. The slag formation isstarted, if so preferred by blowing hot air through the tap hole.

To the solid mixture of preheated steel or iron or both and Slag formingmaterials and carbon, it is practical to pourhot molten pig iron in anydesired quantity into the ladle where, together with the iron and steelwhich had been added in solid form and become melted, the pig iron isrefined. By regulating the temperature and carbon content and adding thedesired alloying elements, it is practical and economical to manufacturealmost any type and grade of steel known at present.

It is also practical with my invention to pour molten pig iron into theladle without the addition of solid iron and to refine the pig iron andmak steel out of it. In such a case in order to decarburize the molteniron, iron oxide is added. The usable generated heat of slag reactionsupplies the heat for the endothermic reaction for reducing the addediron oxide with the carbon contained in thepig iron.

t is thus readily seen that my invention is a new and practical processfor melting andrefining iron and making steel out of it directly,whether the iron is in the form of solid iron and steel scrap alone orin form of molten scrap or molten pig ironor any of their combinations.Furthermore, this is done without addition of external heat after theinitial preheating of some or all of the materials charged.

In the well known process of open hearth refining and melting the sameresults are possible only with the addition at high temperatures oflarge amounts of external heat, which is inefficient. In the open hearthit is also difficult and costly to make steel either from scrap or pigiron alone, and usually a mixture of the two is needed.

In the electric furnace, steel may be made from either or bothseparately but this again requires the addition of external heat in formof electrical energy which for this and other reasons is a costlyoperation.

My process is also easily used for partially refining or refining andmaking into steel iron which has been melted or partially prepared inother types of furnaces. If desirable, the material thus prepared by myprocess may be further treated in other types of furnaces.

In order tofinish the melting of the red. hot scrap or pig iron, about350 B. t. u. is needed per lb. or 700,000 B. t. u. per ton. This amountof heat is furnished by the formation of about 700 lbs. of alumina slag,the formation of which also raises the temperature of the whole chargeto about 3000 F.

The carbon in, the ladle reduces the iron oxide formed on the surface ofthe heated iron. If some such iron oxide is left it will serve forcombining with the phosphorous in the iron and with the slagin'thewell'known manner. If not enough iron oxide is left it can beadded to the molten charge as heavy lumpssinking into the iron bath,causing it toboil while melting 'and'partially re-' ducing and combiningwith the phosphorous. Thus the hot slag forming acids and bases servenot only as source of heat for meltin the iron but also for refining theiron and steel.

The amount of heat to be developed, the amount of lime and alumina sand,and their temperature as well as their composition, are easilycalcualted by any technician versed in the art of melting andmetallurgy, who can also easily determine the amount of carbon and ironoxide, which always depends upon the nature or analysis of the desiredend-product of carbon or steel.

My invention is also a new method of carburizing the hot iron, and ifdesired, carburizing it to a higher degree than it has been heretoforepractical or economical. It is also a new method for attaining differentand highly desirable carbon structures, some of which will be differentfrom any heretofore attained in any comparably economical process.

It is a scientific fact that iron, well above 3900 F. absorbssubstantially more carbon than below this temperature and also that thestructure of the carbon content is much finer, different and moredesirable than the structure that can be obtained below these hightemperatures. The different steel and iron castings made with this finecarbon structure have many desirable characteristics not obtainable orpractical with the coarser carbon structure obtained from carburizationat lower temperature. With the present processes such high temperaturesare either not attainable or not practical, while with my process theobtaining of extreme high temperatures are not only possible butcommercially feasible, practical and economical.

The degree of various high temperatures is controlled and regulatedaccording to the need for a particular carbon structure and otherspecified requirements.

For this purpose, preferably charcoal is place at the bottom of theladle, and hot alumina sand and hot lime are poured or charged on top ofthe carbon. A layer of hot charcoal, coke or carbon in other form ischarged as top layer. When the lid i closed, the molten metal to becarburized is poured in, starting slag formation, The very hot slagcollects on top of the iron and penetrates the charcoal charge. Now theplunger is moved upward and the charcoal is lifted from the molten ironby the heavy, fluid iron and the hot slag surrounds the carbon, heatingit considerably. This superheated charcoal is then pushed down into theiron which absorbs some of the hot carbon. Again the carbon is allowedto lift and is heated by the slag again and then is pushed down into themolten iron again, increasing its temperature and carbon content. Byrepeating the operation any desired number of times the desired degreeor a very high degree of carburization is reached.

The carbon pile may not only be alternately submerged deep into themolten charge and allowed to lift, but may be oscillated up and down sothat it constantly changes its level in the bath and thereby its contactwith the particular layers of metal and slag.

It should be borne in mind that while I have shown a particular type ofplunger for submerging the carbon pile, it is obvious that there aremany other suitable ways and means of accomplishing the same purposewithout departing from my invention. Similarly, any particularconstruction of top, or door or shape of vessel, or gas outlet or otherdetails obviously are not essential to carry out the purposes andoperation of my process, as difierent materials and different productionwill require somewhat different designs. Different designers, buildersor users of equipment will construct the plant in somewhat dilferentways. In some instances the plunger, or even the door may be dispensedwith since a lesser degree of carburization can be achieved by lettingthe carbon pile float in the molten metal or slag. The carbon pile mayalso be pushed down by other simpler means than by a plunger, forinstance by a rod, weight or other device.

My method will also be useful for putting into the metals alloys lighterthan the metals themselves. For instance, by my method magnesia can beadded easily and economically to the iron for alloying the two metals.Lumps or bars or sheets of magnesia are placed on the bottom of theladle and hot carbon lumps are placed over the solid magnesia and thecarbon pile is held down as previously described. The molten iron meltsthe magnesia, absorbs it and becomes alloyed with it. In this way theoxidation of most of the magnesia is prevented, practically all themagnesia is absorbed and the amount is controlled, except for the amountwhich combines with the oxygen contained in the molten iron. The hotcarbon maintains a reducing atmosphere so that there will not be muchtendency for oxidizing the magnesium.

If absorption of carbon is not desired, some very dense carbon such asbroken electrodes or possibly dense refractories may be utilized.

The magnesia may be added without removing the carbon pile. Forinstance, a hole may be made in the center of the pile whereby themagnesia block or lumps may be placed at the bottom and held down by ablock or rod of electrode or of other type of solid carbon or refractorywhile the molten iron is poured down into the pile.

The solid magnesia can also be held down at the bottom of the ladle by asolid carbon rod, column or electrode which preferably has a hollowspace at the bottom, while the molten metal is poured into the ladle.The magnesia will be prevented from floating to the top and thereforefrom becoming oxidized. The molten metal then will dissolve and absorbthe magnesia, part of which will also act to deoxidize the molten metal.

Another method of submerging the reactive light alloy or carbon or theircombination is as follows: The ingredients to be absorbed are placedinto the hollow on the end of a rod and sealed by any suitable substanceeasily dissolved by the hot molten iron such as Wax, pitch or a thick orthin layer of concrete. The rod may be carbon, refractory or simplysteel. The deoxidizer, carburizer or nodulizer or other mixtures arepushed down into the bath and held down until absorbed. The part of thesteel rod is dissolved by the hot metal but by that time the lightestmetals and the carbon will be completely absorbed. At the end of the rodmay also be placed a closed container of easily meltable metal ofsuitable composition. The lower end of the container may be sealed witheasily solvable material so that the molten metal absorbs the contentsof the container before it has a chance to fioat to the surface where itwould become oxidized.

It should be kept in mind that, while for the sake of simplicity andbrevity only magnesia as light metal has been mentioned, neverthelessall other deoxidizing light metals, such as calcium, barium, titanium,cesium, etc. may be used, or

even heavy metals or any combination thereof may be used withoutdeparting from my invention.

The above described method of submerging the deoxiclizing, alloying andother elements into the molten metal bath is not limited in itsapplication to the ladle illustrated, but may be used in any type ofmelting or refining furnace such as an electric furnace, gaseous meltingfurnace, mixing ladle or other device. The ladle Or crucibleconstruction may be such that the top or roof of an electric furnacewill fit over it, in the manner of top charged electric furnaces. Afterthe desired reactions and operations are accomplished in the crucible,the electrodes with the roof may be placed over it, or the cruciblemoved under the electrodes, and further operations practical in electricarc furnaces may be carried out. Thus the electric furnace may bepractically combined with my process for performing the operations astaught by my invention.

Another but similar method of carburizing the metal and at the same timeputting in the deoxidizing light metal or other alloys is as follows:

Finely divided or granular carbon and finely divided or granular metalor metals are mixed and made into briquettes, rods or any other suitableform. If desirable, a suitable hinder or other materials such as lime,alumina, etc. may be also mixed in. This mixture may also be coated withsuitable coating like tar or clay, or may be enclosed into metalliccasing to prevent slow oxidization or even possible ignition. Thebriquettes may have any desired looseness and porosity, or the mixturemay even be kept in a loose state when surrounded by a casing orcoating. These briquettes will then be submerged into the ladle orfurnace as described above. Since the molten iron has a great affinityfor the magnesia and other similar elements mentioned above, it willabsorb the magnesia, leaving the carbon very porous and therebyfacilitating the absorption of carbon also.

The carbon and the alloys or deoxidizers or any of their combinationsmay be so proportioned in the briquettes or pills that they will leavethe desired amount of carbon and the other metallic elements in a moltenor solidified metal. For this reason several different mixtures may bemade from a properly selected combination from which the desiredultimate results of analysis of alloyed metal may be obtained.

A combination of slag forming refractories such as alumina, silica andlime may also be so mixed with carbon that they react with each other inthe molten iron and form slag. The carbon mixed with them is absorbed bythe metal to provide the proper carburization or to add the balance ofcarbon desired. Preferably, mainly alumina and lime should be used asslag forming materials. At the same time the slag forming materials arereacting to form slag, they develop a large amount of heat helping notonly the carburization but also, if desired, the temperature rise of themolten metal as well as the refining of the metal.

This, for instance, will be very important when making iron or steelwith nodular structure, the so-called nodular iron. In the nodular ironthe very low sulphur content is very important. The hot slag formationwhich will cause boiling and agitation of the molten metal will havegreat aifinity for the sulphur, especially if so proportioned that it isstrongly on the basic side. It is also partly due to the hightemperature developed.

Another practical method of preventing reoxidation of the alloys andlight metals in the ladle is so to construct the ladle that reducingatmosphere is maintained in the ladle while pouring the metal into it.The reducing atmosphere may be maintained for instance by covering theladle and keeping it gas tight while blowing reducing gas or neutral gasinto it through a pipe suitably placed into the cover or into the sidewhile pouring molten metal through a hole or spout into the ladle inwhich the above mentioned materials have been previously placed, thuspreventing them from reoxidization.

The same purpose may be accomplished by pouring the molten iron firstinto the ladle and keeping reducing atmosphere over the molten metalwhile adding the above named elements and while those elements are beingabsorbed by the molten bath.

This method is also used for raising the temperature of the molten ironto any desired practical degree. It isinteresting to consider that thespecific heat of slag is about 0.23, that of the carbon is roughly about0.4 while that of the iron only about 0.15 B. t. u./lb. which shows howfavorable the heat quantities are for increasing the temperature of themolten iron or of other metals by following my method of doing it.

Preheated air may also be blown into the carbon bed at any time duringthe operation. This should be done preferably after the pressure on thecarbon is released and it is lifted out of the metal bath. The carbonwill burn with the hot air at a very high temperature making the carbonvery hot. When the carbon is forced down into the metal bath, part ofthe excess heat of the carbon will be transferred to the metal thatagain penetrates the pores of the carbon. Since the temperature increaseenhances the absorption of carbon, the hotter metal will absorb morecarbon when the carbon is very hot than it will when the carbon iscooler.

If even higher temperature of carbon is desired than it is practical toreach with preheated air the air may also be enriched with oxygen, oroxygen alone may be used instead of preheated air. The oxygen is blownin preferably near the contact of carbon pile with the molten iron,

creating very intense localized heat near the metal surface but awayfrom the refractory Wall of the ladle (or of the furnace). Thisintensely heated carbon, when pushed down into the metal bath, will notonly be absorbed more readily by the metal, but also will transfer itsexcess heat to the metal. Thus the carburization will be materiallyaided and intensified, partly by the increase of temperature of themetal and partly and to a greater degree by the much greater temperatureof the incandescent carbon.

Since the specific heat of the carbon is almost three times as much asthat of iron, the heat of the carbon over and above the heat of the ironat a lower temperature of the iron bath will add to a considerableamount to the temperature of iron in contact with the carbon, therebyfurther enhancing the absorption of the carbon.

A considerable but lesser amount of carburization is accomplished, ofcourse, by blowing hot air or oxygen into the carbon more continuouslyover or near to the surface of iron, making the carbon intensely hot. Asthe carbon is absorbed by the iron more hot carbon is pushed down intothe bath. For this type of carburization an up and down motion of theplunger and carbon may be required.

By alternately bringing the carbon to such an intense heat substantiallyabove the temperature of the metal bath and by pushing down the hotcarbon into the bath, not only is the absorption of carbon enhanced butthe temperature of the iron is increased much faster and moreefficiently than by the present method of firing with gas or oil overthe metal surface, as in the case of the open hearth furnace, forinstance. This will be illustrated by a numerical example.

Eighty pounds of pressed carbon occupies about 2 cu. ft. and has about 1cu. ft. of void. When heated, for instance, to 600 F. above thetemperature of the metal and pushed into the metal bath, the 80 lbs. ofcarbon will be penetrated by about 500 lbs. of iron when the temperatureof iron and carbon has become equalized, thereby raising the temperatureof the iron by about 200 F.. By repeating the operation, the temperatureof the iron may be easily and quickly raised by EGO-500 F., withoutexcessive overheating of the refractories and without excessive heatloss.

In releasing the weight of force over the top of the carbon pile andallowing it to rise to the surface there will be some molten iron in thepores and on the surface of the carbon. By blowing hot air or oxygeninto this part of the pile, the iron is oxidized with great speed,allowing the rapid heating of the pile. Of course the molten iron oxideagain will reduce with the hot carbon, but the net result of temperaturestill will be the same as if the oxygen had burnt fully with carbonalone. This is due to the law of conservation of energy. However, theheating will be more intense and the absorption of the carbon by thereducing iron more complete.

When the desired amount and composition molten metal accumulates, it maybe tapped out of the ladle together with the molten slag. The firing ofthe pile may also be done by a pulsating or intermittent repeated blowor stream of air or of oxygen. In this way only part of the iron liftedby the carbon pile will be oxidized. Part of the intense heat developedon the surface of the carbon pieces is transferred to the iron in thepores of the carbon. The hotter iron will absorb more carbon and becomemore fluid, and will drip down into the iron bath carrying with it morecarbon.

By following the above described method some silica can also be reducedfrom the molten slag to silicon which will flow down into the iron bathand will alloy with the iron. Some silica lumps or sand may be chargedwith the charcoal in layers, or scattered in the charcoal which ispreferably ground, near the vertical center line of the furnace orladle. As the charcoal descends the very hot gases and hot carbon willreduce the silica to silicon. The silica may also be charged in a veryhot plastic form or poured in over the top in a molten form. It may alsobe blown into the hot carbon bed through the air or gas inlet in apowdered form by the heated air, oxygen or some other gas. Oxygenespecially will create very intense heat, which combined with the veryhot carbon monoxide and very hot carbon will greatly enhance andintensify the reduction of silica. While any spot in the furnace orladle would be overheated when fired with oxygen, the heat necessary forheating the silica and the heat absorbed by the endothermic reaction ofreducing silica to silicon will cool the carbon bed to a temperaturewhere it will not excessively damage the lining of the surface.

Also manganese and other oxides may be treated in a manner similar tosilica. Any of these oxides may be powdered and mixed with carbon towhich a binder may be added if so desired, and briquettes made from themixture. These briquettes may be gradually charged so that in descendingthey reach the hottest part of the furnace. The ratio of the oxide andcarbon preferably should be such that the amount of carbon will begreater than determined by the stoichiometric ratio for reducing themetallic oxide. The surplus residual carbon will protect the oxide frombeing affected by any slag formation and protect the reduced metal fromreoxidization. It is thus readily seen that my process of repeatedlysubmerging hot carbon into the molten metal and into the slag above itand blowing hot air or oxygen into the carbon pile while it is floatingabove the surface of the metal or slag is used in a practical andeconomical way for recovering the desired metals from the metallicoxides in the molten slag.

My invention is also used as a new method for producing zinc from itsoxides, sulphates or chlorides. The zinc oxide is charged between twolayers of bases and acids consisting preferably of lime and high aluminasand. Molten iron is poured over the mixture. The oxygen of the zincoxide is removed from the zinc by oxidizing the iron, whereupon the zincis vaporized leaving the oxidized iron in the slag. The zinc vapor iscondensed after leaving the crucible. For this purpose the top of theladle or crucible is so constructed that the vapor leaves through a pipewithout leaking into the atmosphere and is condensed. Such constructionneeds no illustration here as it can be designed and constructed by anaverage mechanic from the information and specification heretoforegiven.

The iron oxide is combined in the slag and is reduced from it by carbonin the manner previously shown.

Similarly, zinc sulphate will give up its sulphur to the iron, fromwhich it is oxidized by blowing hot air into the hot slag and replacingthe sulphur in the iron by oxygen. The iron oxide is then combined inthe slag from which it is reduced out by carbon in a manner previouslyshown.

Reducing the iron oxide, manganese oxide and other oxides from the hotmolten slag that is formed in the crucible as shown above is alsoaccomplished when desired in the following way without departing from myinvention.

My invention of utilizing the potential energy of cold or preheatedbasic and acid oxides for forming heat energy in a vessel for meltingmetals and their oxides and gangue materials and forming very hot slagand then reducing some of their metallic oxide content either from theslag or from the hot solids, is also combined with reducing the ironoxide, manganese oxide and silica from the hot slag by blowing hotreducing gas into the slag through the opening 26 in the side of theladle. This reducing gas is either carbon monoxide, hydrogen or thecombination of both. Preferably hot cracked gas is used as it comes fromthe thermal cracker, or hydrocarbon gas containing the carbon black thatis carried out of the checker work of the gas cracker along with the hotcracked gas may be used. The reducing gas as well as the carbon blackreacts with the oxide in the slag or in the sponge iron block. Thereduction of iron oxide with hydrogen and carbon monoxide is exothermicat such temperatures, and adds heat to the slag to further raise itstemperature. Some 21 of the heat produced, however, by the reducingreaction, is carried out by the reacting gas that becomes further heatedin the ladle or crucible before leaving it.

The crucible or ladle may be so constructed that the lid or top is madegas tight, while the gas leaves the crucible through a pipe or stackpreferably through the side of the ladle. The gas leaving the crucibleis utilized for heating if desired, or the steam is condensed and thecarbon dioxide is scrubbed out or reacted to form carbon monoxide whichis preheated and passed back into the crucible as reducing gas.

The top of the slag is preferably covered with charcoal or other carbonthat floats over the top of the slag or stays over the top of thesolids.

. The reducing gas that is blown through gas hole 26 makes the slagfoamy so that it splashes over the charcoal providing more surfacecontact for the reacting oxide and gas. The charcoal layer prevents thefoamy slag or molten oxides splashing or being carried up by the gas.

Some of the oxidized gas reacts with the carbon that cracks the steamand CO2, but this reaction is so cooling that soon the temperature ofthe carbon is lowered and the reaction is stopped. A temperature balanceis established between the carbon and used gas in any operation.

In many instances some reducing gas is passed into the crucible with asudden great velocity so that the slag is made more foamy and splashesover the charcoal covering the charge. The oxide to be reduced thusbecomes more exposed to the action of the reducing gas. This jet of highspeed gas is then followed by a more steady flow of reducing gas,alternating between a jet and steady flow, in a pulsating manner.

My process may also be used to great economic and operating advantagesin connection with .utilizing open hearth, electric furnace and blastfurnace slags to form cement. The refining slag in an open hearthfurnace contains too much iron oxide to be used for cement makingdirectly, and in most cases also contains too much phosphorus. Suchslag, however, may easily be turned into usable and high grade cement byfollowing the teachings of my invention.

After the molten slag is poured ofi or tapped out of the open hearth itis transferred into my ladle for further treatment to extract from itthe iron oxide and phosphorus and some other impurities to any desirabledegree. The proper amount of lime or other bases are added to the slagfor adjusting the composition to obtain the proper cement and to assurereaching the proper temperature for reducing the iron oxide and thephosphorous out of the slag. After this, hot reducing gas is blown orpassed through the slag in any suitable manner. This reducing gas may behydrogen, carbon monoxide or both, and if desired may contain carbon.

It may also be feasible, as previously described, to treat the slag withcharcoal or other carbonaceous reducing material. Whenever the moltenslag contains enough surplus sensible heat to maintain the reducingreaction with carbon, no addition of heat will be necessary. Otherwiseheat may be added by first preheating the carbon before submerging itinto the molten slag, or it will also be practical to produce heat byadding more lime and high alumina content slag forming acids. Thereaction with reducing gas, especially with carbon monoxide, will bestrongly exothermic, and in most cases will not require the addition ofheat.

It will also be practical in most instances not to add any lime to thereducing slag .whether it is from open hearth or from basic electricfurnace, since these slags in most cases contain much lime, usuallyenough to form good cement. If desired, lime may also be added to theslag after the iron and some other oxides are reduced, in order to meetthe desired specification.

Molten blast furnace slag may also be treated by my method by adding therequired amounts of hot or ,cold acids or bases to produce the type ofcement desired. :Sulphur compounds may be burned out by means of hotair, and the various oxides present may then be reduced as previouslydescribed.

What I claim as my invention is:

l. A method of refining metal comprising introducing carbon, lime,alumina and silica into a molten metal bath and holding said materialssubmerged in said bath until said materials are absorbed by said bath.

2. A method of refining metal comprising introducing carbon, lime,alumina and silica into a molten iron bath and submerging said materialsin said bath until said materials are absorbed by said bath.

3. A method of refining metal comprising adding carbon, lime, aluminaand silica to a molten iron bath and maintaining a reducing atmosphereover the molten metal while said elements are being absorbed.

4. A method of refining iron comprising forming briquettes of apredetermined mixture of carbon, lime, alumina and silica, adding saidbriquettes to a molten iron bath and maintaining a reducing atmosphereover the molten iron while said mixture of carbon and slag is beingabsorbed.

5. A method of refining iron comprising forming briquettes of apredetermined mixture of carbon, lime, alumina and silica, adding saidbriquettes to a molten iron bath, and holding said briquettes submergedin said bath until the carbon is absorbed and the slag is formed.

6. A method according to claim 5 wherein a deoxidizing atmosphere ismaintained over said molten iron bath.

7. A method according to claim 5 wherein additional alloying materialsare included in the briquette.

8. A method of refining iron comprising charging carbon, lime, aluminaand silica into a ladle, pouring molten iron over said materials, andmaintaining a reducing atmosphere in the ladle while said chargedmaterials are being absorbed by said molten metal.

9. A method of producing calcium aluminate slag comprising chargingalternate layers of carbon, lime and alumina sand into a ladle, pouringmolten metal over the charge to start the slag forming reaction andgenerate heat, and maintaining proper reducing conditions andtemperature within the ladle to effect reduction of oxide impurities totheir respective metals.

10. A method of producing calcium aluminate slag comprising chargingcarbon, lime and alumina sand into a ladle, pouring molten metal overthe charge to start the slag forming reaction and generate heat therebyproducing molten slag, and submerging the carbon in said molten slag toeffect reduction of oxide impurities to their respective metals.

11. A method of producing calcium aluminate which is substantially freefrom silica comprising charging preheated carbon, lime and a mixture ofalumina and silica into a ladle, introducing oxidizing gas into thecarbon to generate heat thereby, causing the lime to react with saidalumina and silica to generate additional heat and produce molten slag,and then submerging the carbon in said molten slag while maintaininghigh temperature to efiect reduction of said silica to silicon.

12. A method of producing calcium aluminate comprising chargingpreheated carbon, lime and a mixture of alumina and silica into a ladle,introducing oxidizing gas into the carbon to generate heat therebycausing the lime to react with said alumina and silica to generateadditional heat and produce molten slag, heating carbon substantiallyabove the temperature of molten slag to supply heat balance for reducingthe silica to silicon, and then submerging heated carbon into the slag,permitting carbon to rise to the top of the slag, reheating the carbonand resubmerging and continuing the alternate heating and submerging ofthe carbon until iron oxide and silica are reduced.

References Cited in the file of this patent UNITED STATES PATENTS NumberNumber Number 24 Name Date Bessemer Aug. 1, 1871 Reeves June 5, 1888Fleischer Apr. 12, 1892 Myer Aug. 21, 1894 Uehling July 23, 1895 SaniterMay 4, 1897 Tone Dec. 8, 1908 Peacock Aug. 8, 1911 Machalske May 27,1913 Gostling Mar. 24, 1914 Levy Mar. 25, 1919 V05 Oct. 2, 1923 EckelMay 5, 1925 Eckel July 6, 1926 Ruder June 28, 1927 Runyan Apr. 17, 1928McCausland Sept. 10, 1929 Neuhauss Sept. 13, 1932 Barstow Feb. 21, 1933Badger Nov. 14, 1933 Fleming Jan. 6, 1948 FOREIGN PATENTS Country DateGreat Britain of 1890 Great Britain of 1909

1. A METHOD OF REFINING METAL COMPRISING INTRODUCING CARBON, LIME,ALUMINA AND SILICA INTO A MOLTEN METAL BATH AND HOLDING SAID MATERIALSSUBMERGED IN SAID BATH UNTIL SAID MATERIALS ARE ABSORBED BY SAID BATH.